Creating a custom listener for a Backbone View

Question

Creating a custom listener for a Backbone View

As someone who is just starting out with javascript and Backbone.js, I am trying to figure out how to bind a custom listener to a Backbone view when it is initialized. For example, I want to achieve the following:

var CampaignListView = Backbone.View.extend({
    initialize: function(){
       this.on("customFunc")
    },
    customFunc: function() {
        if (this.$el.scrollTop() == 500 ) {
             console.log("this has occurred, time to do stuff")
          }
    }
)}

I'm looking for a way to trigger some code every time a user reaches a specific scroll position.

Any help would be greatly appreciated. Thank you!

javascript backbone.js

Answer 1

Answer №1

Are you looking for a way to trigger an action when the window scrolls? If so, there are a couple of approaches you can take:

The first method involves using the remove function to clean up the event binding:

var CampaignListView = Backbone.View.extend({
    initialize: function(){
       // Consider adding an identifier to the event name, such as 'scroll.campainlist'
       $(window).on('scroll', _.bind(this.customFunc, this));
    },
    customFunc: function() {
        if (this.$el.scrollTop() == 500 ) {
             console.log("Action triggered upon scroll")
          }
    },
    remove: function() {
      $(window).off('scroll');
      Backbone.View.prototype.remove.call(this);
    }
)}

Another option is to utilize an Event Aggregator concept like this:

var vent = _.extend({}, Backbone.Events);

$(window).on('scroll', function(ev) {
  vent.trigger('window:scroll', ev);
});

var CampaignListView = Backbone.View.extend({
    initialize: function(){
       this.listenTo(vent, 'window:scroll', this.customFunc);
    },
    customFunc: function() {
        if (this.$el.scrollTop() == 500 ) {
             console.log("Action triggered upon scroll")
          }
    }
)}

Answer 2

Are you looking for a way to trigger an action when the window scrolls? If so, there are a couple of approaches you can take:

The first method involves using the remove function to clean up the event binding:

var CampaignListView = Backbone.View.extend({
    initialize: function(){
       // Consider adding an identifier to the event name, such as 'scroll.campainlist'
       $(window).on('scroll', _.bind(this.customFunc, this));
    },
    customFunc: function() {
        if (this.$el.scrollTop() == 500 ) {
             console.log("Action triggered upon scroll")
          }
    },
    remove: function() {
      $(window).off('scroll');
      Backbone.View.prototype.remove.call(this);
    }
)}

Another option is to utilize an Event Aggregator concept like this:

var vent = _.extend({}, Backbone.Events);

$(window).on('scroll', function(ev) {
  vent.trigger('window:scroll', ev);
});

var CampaignListView = Backbone.View.extend({
    initialize: function(){
       this.listenTo(vent, 'window:scroll', this.customFunc);
    },
    customFunc: function() {
        if (this.$el.scrollTop() == 500 ) {
             console.log("Action triggered upon scroll")
          }
    }
)}

Answer 3

Answer №2

If you want to leverage the power of delegateEvents in Backbone Views, one option is to listen for the scroll event within your view. Keep in mind that this event will trigger with every scroll action. I have created a simple JSFiddle here based on your scenario. Take a look at some of the JavaScript code below, specifically how events{} are used.

var CampaignListView = Backbone.View.extend({
    el: '#list', 

    events: {
        'scroll': 'customFunc'    
    }, 

    initialize: function() { }, 

    render: function() {
        this.$el.html(sampleHtml);
        return this; 
    }, 

    customFunc: function() {
        // console.log('scrolling... top is ' + this.$el.scrollTop()); 
        if (this.$el.scrollTop() >= 100 ) {
          console.log("this has occurred, time to do stuff")
        }
    }
}); 

var view = new CampaignListView(); 
view.render();

Answer 4

If you want to leverage the power of delegateEvents in Backbone Views, one option is to listen for the scroll event within your view. Keep in mind that this event will trigger with every scroll action. I have created a simple JSFiddle here based on your scenario. Take a look at some of the JavaScript code below, specifically how events{} are used.

var CampaignListView = Backbone.View.extend({
    el: '#list', 

    events: {
        'scroll': 'customFunc'    
    }, 

    initialize: function() { }, 

    render: function() {
        this.$el.html(sampleHtml);
        return this; 
    }, 

    customFunc: function() {
        // console.log('scrolling... top is ' + this.$el.scrollTop()); 
        if (this.$el.scrollTop() >= 100 ) {
          console.log("this has occurred, time to do stuff")
        }
    }
}); 

var view = new CampaignListView(); 
view.render();

Creating a custom listener for a Backbone View

Answer №1

Answer №2

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